The present invention relates to a process for optimized bandwidth allocation for guaranteed bandwidth services within telecommunications networks, in particular a method and a system for minimizing bandwidth allocation for alternative routes of guaranteed bandwidth services.
In recent years, the fast growing of telecommunications networks and the large amount of services over such networks have led to a remarkable growth of traffic. It is fundamental to provide to some of the services using a telecommunication network a certain level of service, for example by guaranteeing in advance predefined service transmission rates. A service hereby indicates an object in the network management system which is used to model a customer service. To each service it is assigned a certain traffic class (TC) which allows to group different services according to TCs. In order to cope with the need of guaranteeing in advance predefined service transmission rates, a service can be assigned to a guaranteed bandwidth TC so that the management system reserves bandwidth for the network resources used for the service.
In carrier grade Ethernet networks, as well as in SDH/SONET and ATM networks, a high service availability is required. High service availability is guaranteed when a network fulfils certain requirements. The first requirement is that the network capacity is managed in the management system in order to avoid overbooking for guaranteed bandwidth (GBW) services. The second requirement is that a service can be protected within the network. The service protection concept ensures that, even in case of a failure in one of the elements or links of the network, the service traffic is nonetheless transmitted. The term link refers to the physical or logical connection between two ports or network elements. The third requirement is that for each GBW-service, a bandwidth for that specific service can be assigned in the network. The forth requirement is that for each GBW-service, one or several dedicated routes can be assigned in the network: only one route is assigned, the so called active route, when the service is meant to be “unprotected” and several routes are assigned, one active route and N alternative routes, when the service is meant to be protected in case of single point of failure (SPOF) in the network. The number N of the alternative routes to be assigned depends on the topology of the network and on the number of SPOFs which can be protected.
According to widely used methods, in order to protect a GBW-service, the bandwidth for the active route as well as for each one of the alternative routes of the service is reserved in the management system. Unfortunately, in such methods, the reserved bandwidth grows linearly with the total number of routes of a service (linear bandwidth reservation approach). The active route of a service is hereby defined by the route via which the service traffic is transmitted in case there is no failure in the network. The active route basically corresponds to the initially planned route. The alternative routes of a service are the routes calculated taking into account the failure of a network resource used by the active route of the service. Such alternative routes ensure that the service traffic is transmitted through the network even in case of such network failure. The alternative routes are the so-called protecting routes of a service: the routes that guarantee that, in case of network of failure, a service can be protected elsewhere.
Widely known methods for calculating the service routes of an Ethernet network are based on algorithms belonging to the spanning tree protocol family (xSTP). Spanning tree protocol (STP), rapid spanning tree protocol and multiple spanning tree protocol (MSTP) are examples of widely used protocols belonging to the xSTP family.
In high service availability networks, the network management system ensures that the capacity of the network resources used for GBW-services is not overbooked. The routes are configured in the network by VLAN assignment of the ports, which are used for the active as well as for the alternative routes. Unfortunately, due to the fact that, in the linear bandwidth reservation approach, the bandwidth is reserved for all the routes, i.e. for the active as well as for each alternative route, a major drawback is that a large quantity of bandwidth is required for service protection and, as a consequence, transmission capacity is wasted.
At present, in order to guarantee that GBW-services are not overbooked, the user has to keep track about all the services already configured in the network and check if there is enough network capacity left so that a new GBW-service can be configured and added to the network. Depending by the approach used for reserving bandwidth for the protecting routes, the user has to calculate how much bandwidth to reserve to ensure service protection. This procedure has the drawback that high operative expenses are needed due to the complexity of the required calculations. An alternative widely used method, in order to avoid that GBW-services are overbooked, is to allocate enough network capacity by abundant provisioning of bandwidth in the network. However, this second method has the drawback that high capital expenses are needed due to the required investment for acquiring additional network resources.